"Katy expected that Taylor would post something about it, but she didn't expect the actual letter to go on social," an insider told The Sun on Wednesday. "The thing is, you can only see part of what Katy wrote and it looks like she's taking sole responsibility for the entire feud.

Taylor and Katy in 2011. (Getty)

"Without context, it looks like she's taking the blame for everything and obviously there's a lot more to it than that."

On Tuesday, Perry sent Swift, 28, a literal olive branch and an apology letter.

The 'Look What You Made Me Do' singer then shared a video of the package on Instagram Stories, which she captioned "Thank you Katy" with a heart emoji.

"I just got to my dressing room and found this actual olive branch," Swift said in the video. "This means so much to me."

In the video, the partially obscured letter can be seen peeping out of an envelope and reads: "Hey Old Friend -- I've been doing some reflecting on past miscommunications and hurt feelings between us." The words "deeply sorry" and "clear the air" are also in the letter.

According to The Sun's insider, Perry was "surprised" to see the letter in Swift's Instagram Stories as they hadn't discussed the contents of the letter going public.